Electrostatic printing apparatus



United States Patent [72] Inventor Ira M. Sage 2,854,947 10/1958Giaimo,lr. l 17/17.5X New York,N.Y. 2,904,000 9/1959 118/637 [211 Appl.No. 816,452 3,108,346 10/1963 335/302X [22] Filed Feb. 17, 19693,135,433 6/1964 222/231X Division of Ser. No. 295,652. July 17.3,211,966 10/1965 335/302 1963, Pat. No. 3,451,320. 3,245,381 4/1966Brenneisen et a1. 118/637 [45] Patented Dec. 15, 1970 3,233,587 2/1966Morton 118/637 [73] Assignee lnq. C. Olivetti & C.,S.p.A. FOREIGNPATENTS lnrea, Italy an Italian corporation 1,093,025 1 1/1960 Germany335/302 Primary ExaminerPeter Feldman Attorney-Curtis, Morris andSafford [54] ELECTROSTATIC PRINTING APPARATUS 9 Claims, 24 Drawing Figs.

[52] U.S.C| 118/637; ABSTRACT: Latent electrostatic images are developedby 1 7/175: 222/231 means of a magnetic brush having a plurality ofwashers, each [5 l Int. Cl. B051) 5/02 hem along the lines f polygonmounted on a rotary shaft In [50] Fleld ofsearch 118/637, 7, effect theSurface of the washers oscillate hack and forth H; 1 17/175; 222/161,56, 231, 232; 335/302 along the image-bearing surface, so that themagnetic brush [56] Rate C1 ed moves back and forth and thoroughlydevelops the latent l image when the washers are rotated. A tonerdispenser dispen- UNITED STATES PATENTS ses toner powder into a mixtureof toner and carrier particles, 1,319,534 9/1919 Robertson 222/231 in anamount metered by the effective oscillation of the brush- 2,786,4403/1957 Giaimo,.lr. 117/17.5X forming washers. In an alternativeembodiment, the brush is 2,826,168 3/1958 Grant, Jr. 1 18/637 formed bya tube made of magnetic material and having holes 2,846,333 8/1958Wilson .1 ll8/637X arranged in aspiral pattern.

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/R/J H. 5066' ATTORNEKS ELECTROSTATIC PRINTING APPARATUS This is aDivision of U5. Application Ser. No. 295,652, filed .Iul. I7, l963,nowU.S. Pat. No. 3,451,320.

This invention relates to electrostatic printing apparatus. Moreparticularly, this invention relates to a compact and portableelectrostatic office copier for copying documents on photosensitizedsheet material.

An object of this invention is to provide electrostatic printingapparatus that produces clear and accurate printing quickly at a lowcost.

Another object of this invention is to provide an electrostatic copyingmachine which is relatively inexpensive to manufacture, occupiesrelatively little space, can be moved from place to place withoutpermanent installation, and produces copies of documents at a low cost.

A further object of this invention is to provide such a copying machinewhich is convenient and simple to operate, requires little maintenance,and operates with a high degree of reliability. I

Other objects, aspects and advantages of the present invention will bepointed out in, or apparent from, the following description anddrawings, of which:

FIG. 1 is a schematic view, partly in section, partly in elevation, andpartly in phantom, of an embodiment of the copying machine of thepresent invention.

FIG. 2 is an enlarged detail drawing of a portion of the machine shownin FIG. 1.

FIG. 3 is a schematic drawing of an electrical circuit for the copyingmachine shown in FIG. 1.

FIG. 4 is a schematic drawing of the drive system of the copying machineshown in FIG. 1.

FIG. 5 is a right side view of the machine shown in FIG. 1.

FIG. 6 is a left side view of the machine shown in FIG. 1.

FIG. 7 is a front view of the lamp used with the copying machine shownin FIG. 1. I

FIG. 8 is a sectional view taken along line 8-8 of FIG. 7.

FIG. 9 is a front view of the fuser unit used in the copying machineshown in FIG. 1.

FIG. 10 is a sectional view taken along line 10-10 of FIG. 9.

FIG. 11 is a partially cutaway top planview of the fuser shown in FIG.9.

FIG. 12 is an end view of the knife unit used in the copying machineshown in FIG. 1. I

FIG. 13 is a plan view of the knife unit shown in FIG. 12.

FIG. 14 is a view taken on line 14-14 of FIG. 13.

FIG. 15 is a view taken on line 15-15 ofFIG, '13.

FIG. 16 is a schematic and partly sectional view of the developer unitused in the copying machine shown in FIG. 1.

FIG. 17 is a sectional view taken on line 17-17 of FIG. 16.

FIG. 18 is a view partly in plan, partially cutaway, and partly inlongitudinal horizontal section, of the developer unit shown in FIGS. 16and 17.

FIG. 19 is a view in vertical section taken on line 19-19 of FIG. 18.

FIG. 20 is a plan view, partly broken away, of a brush core used in thedeveloper unit shown in FIGS. 16 through 19.

FIG. 21 is a schematic drawing of another embodiment of the presentinvention.

FIG. 22 is a schematic isometric representation of the copying machineshown in FIG. 21, but with parts broken away for clearer showing.

FIG. 23 is a detail view in vertical section of an alternativeconstruction of a portion of the developer unit of the copying machineshown in FIGS. 21 and 22. 1

FIG. 24 is a detail vertical sectional view taken along line 24-24 ofFIG. 23.

Referring to FIGS. 1 and 2, a document'SO to be copied is inserted intothe copying machine through the lower passage 52 of an inlet guide withthe surface to be copied facing upward. At the end of the passage theforward edge of the document meets a pair of rolls 56, 58 which feed thedocument forward. A curved guide 60 bends it over and into another pairof rolls 62, 64. Rolls 62, 64 feed the document through an expositizedsheets, each of which is fed individually into the machine along withthe document, or upon photosensitized paper fed from a roll and cut tolength within the machine; The machines operator may select betweenthese modes simply and quickly by operating a selector switch located onthe outside of the machine.

The upper passage 72 of the inlet guide is used to guide precut sheets74 of photosensitized copy paper into the machine when the precut sheetmode of operation is selected. It is desirable that the leading edges ofsuch precut sheets be synchronized in the copier with the correspondingedges of the documents to be copied. This is most simply achieved byaligning the edges of the document and sheet before inserting either;then, holding them together at a distance from the leading edges, onespreads them apart just enough to feed the document into the mouth ofpassage 52 and the copying paper sheet into the mouth of passage 72.When the document and copy sheet are inserted into the machine in thismanner, the leading edge of the document 50 depresses a pair of feelerswitch fingers to start the machine's operation. Almost simultaneously,the copy sheet engages in the bight of rolls 76, 78 to start its journeyupwardly to the printing apparatus of the machine. The document thenpasses on to the bight of document-transfer rolls 56, 58 and out of themachine as described above.

Photosensitized paper suitable for making copies in the machine isshown, for example, in US. Pat. No. 3,052,540 to H. G. Grieg. One whichI have found particularly suitable can be made, for example, by coatingpaper with a mixture of an insulating binder, photoconductive pigment,e.g. zinc oxide, and a dye or dye combination to give panchromaticsensitivity. This coating is essentially nonconductive when in the darkor weak light, but becomes electrically conductive when exposed tostronger light. Since the coating is panchromatically sensitive, thedocument 50 may be any flexible sheet material bearing lines and/orcharacters of any desired color or colors.

As exposure to light and shadow may deteriorate such paper, it should beprotected from strong light, and especially from nonuniform light.Protection from such light while the paper is passing through themachine may be provided by a light-tight housing for the entire machineor by shielding enclosing the papers path.

Sheet 74 is moved by the driven rolls 76, 78 onward along a curved guide80, and through a knife unit 82, which cuts copy paper to length duringthe roll-feed operation of the machine but performs no function whenprecut sheets are used. Sheet 74 then moves on to another pair ofrollers 84, 86 which feed the sheet through an electrostatic chargingunit 88. This charging unit comprises a corona discharge device, such asthat shown in [1.5. Pat. No. 2,922,883, which establishes a uniformnegative charge on the coated surface of the copy paper passing throughit.

The sheet 74 is then engaged by a pair of rollers 90, 92 and fed out ofcharging unit 88 past an image location 93, between a backing guideplate advantageously made of metal, 94, and a glass plate 95.

Guide rolls 76, 78 and 84, 86 are interconnected or synchronized withrolls 56, 58 and 62, 64 so that at the instant the sheet 74 reaches theimage location 93, the document 50 likewise reaches the exposure window66'. This exposure window includes a backing guide plate 96,advantageously of metal, and a lower guide plate 98, advantageously ofglass. A lamp is positioned below glass plate 981:0 illuminate the lowersurface of document 50 as it passes the exposure window 66.

Three mirrors 102, 104 and 106 are used to reflect the image of document50 through a focusing lens system 108 and through the glass plate 95onto the sensitized sheet. Each of these mirrors is set at an angle of45 to direct the light onto glass plate 95 and is advantageously of thefirst-surface" type; that is, it has a reflective surface exposed to theincident light. The lens 108 is placed in the path of the image-forminglight, e.g. between mirrors 104 and 106 and is adjusted to focus theimage upon the sensitized sheet 74 at the image location 93.

Sheet 74 when driven past image location 93 is synchronized withdocument 50 moving past the window 93 so that the image of document 50projected upon sheet 74 remains fixed relative to sheet 74 throughoutits travel past the location 93.

In this manner the charged photosensitive surface of sheet 74 isdifferentially discharged by a light pattern corresponding to that ofthe illuminated surface of document 50. In the areas where light strikesthe charged surface of sheet 74 the coating becomes conductive and thecharge is dissipated, while the charge remains on the dark areas, thusleaving a charge pattern corresponding to the dark markings on document50.

An adjustable screen 110 is positioned below glass plate 98 in order toadjust the total light received from window 66 to form the focusedmoving image at 93. The area of the plate 98 in which this screenintercepts light is adjustable to vary the time required for exposure ofthe copy paper to the focused image of the document at 93 and, hence,the strength of the electrostatic image on sheet 74.

Sheet 74, now bearing the electrostatic image, moves on to rolls 112,114 which feed the sheet into a developer unit 118 (see also FIGS. 1619described in greater detail below). In

' the unit 118 developer powder is uniformly distributed across theimage-bearing surface of sheet 74 under conditions such that it is heldon the sheet only where a charge exists.

This powder is composed of a fusible printing material such, forexample, as a thermoplastic resin mixed with carbon black, or other darkpigment or dye, which is positively charged. This powder is brushed ontothe image-bearing surface where the charged developer particles areattracted to and held by the oppositely charged areas on the sheetcorresponding to dark areas on the document. Powder particles touchingdischarged areas are not held, but pass on or fall away. Thus, the sheet74, when it emerges from the developer unit 118, has on its surface avisible pattern of adhering developer particles. This gives a sharp andclear reproduction of thedocument 50.

The darkness of this pattern depends upon the amount of powder held bythe electrostatic image. The amount of powder so held in each areadepends in turn upon the degree to which the area has been dischargedand, consequently, upon the whiteness or darkness of the correspondingarea on the. document and the intensity of light from source 101) andthe amount of such light which is allowed by screen 110 to reach thedocument. Light screen 110 therefore serves as a means for controllingthe darkness of copies made in the machine.

Sheet 74, now bearing a fusible developer powder image of thedocument50, emerges from the developer unit 118 and passes between the outsidesurface of a rectangular-shaped backing tube 119 and a fuser unit 120.Fuser unit 1211 has a radiant heat source 122 and heat reflector 123which heats the developer powder pattern and fuses it into the copypaper to produce a finished copy having a permanent, sharp and clearreproduction of the document.

The finished copy is next fed arounda curved guide 124 which guides thecopy over a transport roll 126, an outlet guide plate 128, and out ofthe machine. A tray or other appropriate means may be attached near theoutlet opening to catch copies as they emerge.

.As was mentioned above, the machine illustrated is equipped for usingeither precut sheets of copy paper inserted into passage 72 or copypaper dispensed from a roll. Such rollfed copy paper 130 is stored in aroll 132 which is rotatably mounted on a hub 133 and stored in alight-excluding com partment 134 in the machine. When the machine'soperator selects the automatic roll-feed mode of operation for themachine, driven feed rolls 136, 138 withdraw copy paper from the roll132 through a dispensing slot 140 in compartment 134 and feed the paperupwardly around curved guide 142, past knife 82, which cuts the paperinto lengths corresponding to those of documents being copied, and on torolls 84, 86 and the printing apparatus of the machine. This printingapparatus performs the same functions on such machine-cut sheets as onprecut sheets fed through passage 72.

This roll-feed mode of operation is semiautomatic in that the operatorneed not feed in copy paper when he inserts the document into themachine; all he needs to do is insert the document and wait a short timefor his copy to emerge. The electrical circuitry used to provide thissemiautomatic operation will be described in greater detail below.

For making multiple copies of a document, a curved repeater guide 143(shown fully in FIG. 2 and in dashed lines in FIG. 1.) is attachedbetween the input end of document passage 52 and the outlet side ofrollers 68, 70. Guide 143 turns the document back into the passage 52 tobe recopied, as many times as desired.

Guide 143 is advantageously made of a stiff resilient sheet material andsecured to the housing of the copying machine at its midportion by meansof a pair of tabs 141. The resiliency of the material of guide 143biases its ends away from one another. A toggle linkage 139 pivotallyconnects these ends of guide 143 together, and a cam 137 is pivotallymounted near linkage 139. Cam 137 can be turned by the machines operatorto the position shown in FIG. 4 so that it does not engage with linkage139. In this position the links of linkage 139 are aligned with oneanother and the ends of guide 143 are positioned to receive the document50 from rolls 68, 70 and guide it upward into passage 52 to berecirculated and recopied. When cam 137 is turned into engagement withtoggle linkage 139, the ends of guide 143 are drawn inwardly by linkage139 and permit the document to exit from the machine in the mannerdescribed above.

Since the sensitivity of the copy paper may be impaired by exposure tolight, the paper storage compartment 134, is substantially light-tightand has nonreflective inner surfaces, eg an anodized black coating usedto line the feed slot 140 as is common in photography. Advantageously,as many of the other interior parts of the machine as practicable aremade dark to absorb any stray light.

A centrifugal blower 144 (top of FIG. 1), driven by an electric motor145 blows air through a duct 146, past the fuser unit 120, and throughthe tube 119 to cool these components and avoid overheating of thecopies. A smaller duct 147 (FIG. 1) feeds air from duct 146 to cool lamp100.

ln FIG. 3 is a diagram showing the interconnection of the electricalcomponents used in the copying machine of FIG. 1. These components areenergized from an AC power supply 148, e.g., a standard 120 volt, 60cycle power supply, through an on-off switch 151) and a fuse 152. ThisFIG. shows the circuit as it is initially, before any document has beeninserted into the machine, but with on-off switch closed to turn on" themachine.

As shown in F168. 1 and 2, a starting switch 154 is located belowpassage 52 of inlet guide 54. Switch 154 has a pair of side-by-sidefeeler" type contact arms 156 and 158 extending upwardly into passage152. These contact arms 156 and 158 are lightly biased in the upwarddirection to contact their upper terminals, as is shown in FIG. 3. Arms1545 and 158 are depressed substantially simultaneously by the leadingedge of a document 50 which is inserted into the machine. The depressionof arms 156 and 150 causes them to contact the lower terminals of switch154 and energize the printing and feeding components and the roll-feedapparatus of the machine, as will be described below.

A shutoff feeler switch 164 is located below outlet guide 128 at the topof the machine, as is shown in FIG. 1. Switch 64 has a contact arm 166which extends into the outlet passage near guide 128. Arm 166 is lightlybiased upwardly to contact the upper terminal of switch 164 and isdepressed by a finished copy emerging from the exit of the machine.Switch 164 shuts the machine off when the finished copy has exitted fromthe machine and no document is being copied.

Referring now to FIG. 3, a manually operated switch 168 serves as ameans for selecting precut sheet or roll-feed operation of the machine.Selector switch 168 connects terminal 160 of switch 154 to contact arm158. By closing switch 168 roll-feed operation is selected and byopening it precut sheet operation is chosen.

Assuming that selector switch 168 has been opened to provide for precutsheet operation of the machine, when a document is inserted into passage52 it depresses arms 156 and 158 of starting switch 154. However, sinceselector switch 168 is open, the depression of arm 158 has no effect onthe operation of the machine. The depression of arm 156 causes it tocontact terminal 160 and connect a coil 170 of a rachet relay 172 to thepower supply 148. When coil 170 is energized in this manner, it pullsarm 178 into contact with terminal 188 and connects the coil 174 of apower relay to the power supply 148. This causes contact arm 180 ofrelay 176 to be pulled into contact with terminal 190 and connects theelectrical printing and feeding components of the machine. Thesecomponents consist of a paper roll drive motor 182, fuser heatingelement 122, lamp 100, a source of high voltage 184 for electrostaticcharging unit 88, and a blower motor 145.

Relay 172 is used to maintain the energization of coil 174 of relay 176and keep the printing and feeding components of the machine energizeduntil the machine is shut off by relay 164. Relay 172 is a standardrachet relay whose contact arm 178 is mechanically held in one positionuntil its coil 170 receives an electrical pulse. The contact arm 178 ofthis relay is switched into contact with the opposite terminal of therelay only when such an electrical pulse is received. Hence, when arm156 of starting switch 154 is depressed, it suddenly connects coil 170of rachet relay 172 to the power supply, thus pulsing the coil andclosing the relay. However, relay 172 does not open when arm 1S6 risesafter the document has moved past it because arm 178 is mechanicallyheld in place. This maintains the energization of coil 174 of relay 176and the energization of coil 170 of the rachet relay is removed.I-lowever, relay 172 remains closed because its contact arm ismechanically held in place.

When the finished copy moves past arm 166, it rises and connects coil170 to power supply 148 through the contacts of relay 172 itself. Thispulses coil 170 and causes relay 172 to open and deenergizes coil 174 toshut off the printing and feeding components of the machine.

When the operator of the machinecloses selector switch 168 to select theroll-feed mode of operation, the operation of the electrical circuit isessentially the same as described above except that arm 158, which isdepressed almost simultaneously with arm 156, makes contact with asolenoid 186 which causes a clutch (to be described below) to engage andthereby cause rollers 136 and 138 (FIG. 1) to be driven and initiatefeeding of copy paper 130 from roll 132 upwardly into the printingcomponents of the machine. Copy paper is fed from roll 132 until thetrailing edge of the document passes over arms 156 and 158 and allowsthem to rise. Arm 158 then connects a pulse network 194 to the powersource 148 through rachet relay 172. Upon being so connected to thepower source 148, pulse network 194 delivers an electrical pulse to asolenoid 196 which causes a single revolution clutch (to be describedbelow) to engage and thereby actuate the knife unit 82 to cut the copypaper to a length approximately equal to the length of the document 50.

Pulse network 194 consists of a silicon'junction diode 198 connected inseries with a capacitor 200 which is connected in parallel with adischarge resistor 202. The transient direct current which surgesthrough capacitor 200 when the pulse network is first connected to thepower supply 148 is the electrical pulse output of the network. 1

The position of switch 154 in passage 52 is adjusted so that thedistance between feeler arms 156 and 158 and the entrance of exposureapparatus 66 is substantially equal to the distance between the cuttingedge of knife unit 82 and the entrance of exposure station 93. By thisadjustment, the length of paper cut off by knife 82 will be equal to thelength of the document 50 being copied.

The drive mechanism of the copying machine is shown in FIGS. 4, 5 and 6.Referring to these FIGS, drive motor 182 and its cooling fan 214 aremounted in the lower portion of the copying machine (see FIG. 5). Theoutput shaft of motor 182 is connected to intermediate documenttransport roll 62 located at the input end of exposure window 66.

In the example illustrated, all drive connections have a oneto-one ratiounless specifically stated otherwise.

A gear wheel 224 is secured to one end of roll 62 (FIG. 4). This mateswith a similar gear 226 on feed roll 58 at the end of document passage52. At the opposite end of shaft 62 is attached toothed pulley 228 whichis coupled by means of a timing belt 230 to a pulley secured to roll 68at the output end of the window 66. Another pulley 234 attached to shaft62 drives roll 78.

' A larger pulley 240, approximately twice the diameter of the pulleyon'246, is connected through a belt and a clutch 246 to a shaft 248 towhich is attached a pair of eccentric cams 250. These cams actuate theknife 82.

Clutch 246 is a single-revolution clutch, and has a tab 254 which isengaged by a plunger 256 of a solenoid 196 to release the clutch inorder to prevent the knife 82 from cutting until the plunger 256 ofsolenoid 196 is lifted to cause clutch 246 to engage. Such a clutch issold under the trade name Tiny clutch by Taylor-Helander ManufacturingCompany.

Roll 78 is connected by belt and pulleys to roll 86, which is locatedimmediately above the knife 82 Roll 78 is geared to roll 138 locatedjust below the knife 8. A second Tiny clutch 270 has a tab 272 (FIG. 5)which is engaged by a plunger 274 of solenoid 186 to disengage theclutch. When plunger 274 is moved back to a position inwhich it does notengage tab 272, clutch 2711 is engaged and rolls 136 and 138 are drivento dispense a measured amount of copy paper from roll 132.

The opposite end of roll 86 is coupled to roll 92 positioned immediatelyabove the charging unit 88 (see FIGS. 4 and 6). Roll 92 is also coupledto roll 114 positioned above the image location 93. The opposite end ofroll 114 is coupled to roll 126 located adjacent output guide 128 andcurved guide 124. Shaft 114 is geared to a magnetic toner brush 300which brushes toner powder onto the electrostatic image on the copypaper. The gear 296 is advantageously somewhat larger than the gear on114 so that the peripheral speed of brush 3110 is somewhat greater thanthe speed of the copy paper moving past the brush. 7

Lamp 100 is shown in detail in FIGS. 7 and 8. An iodinefilled lamp tube302 is mounted in a reflective housing 306, which is mounted on theinside wall of the copying machine, as shown in FIG. 1. Two or moretubes may be used, if desired.

Fuser unit 120 is shown in detail in FIGS. 9, 10 and 11.

' Referring to these FIGS., fuser unit 120 consists of a housing 331 bymeans of receptacles 346. Electrical connections to heating element 122are made at clamps 339. A pair of mounting brackets 350 are provided formounting fuser unit 124 in the copying machine as shown in FIG. 1.

FIGS. 12 through 15 show the knife unit 82 in detail. Referring to theseFIGS., a base block 358 having a pair of semicylindrical grooves 360(see FIG. 14) is bolted to a top block 368 and held spaced therefrom byseveral spacer blocks 374. A knife blade 370 is positioned between baseblock 35% and blocks 374. Blade 370 also has a rectangular slot 376 ateach end forming projections 380 at the rear portion of the blade. Coilsprings 384 are fitted into grooves 360 and slots 376 so as to abutprojections 380. Blade 370 has a pair of indentations 392 at its rearedge for receiving the edges of cams 250.

A shear block 395 having its front edge formed to a cutting edge isaffixed to base block 358 by bolts 462 (FIG. 13). A slot 410 is formedby a pair of spacers 411 between the blade-carrying base block 358 andthe shear block 395. Slot 410 (see also FIG. 1) permits the passage ofcopy paper through the knife 82 until the paper is cut. The front endsof springs 384 abut upon the front edge of block 356 to provide a springreturn for blade 370 after it has completed a paper cutting cycle.

When it is required to cut paper passing through knife 82, solenoid 196(see FIG. 4) is actuated by pulse network 194 (see FIG. 3) to pull itsplunger 256 up and allow clutch 246 to engage shaft 248 for onerevolution and thereby turn cams 250 through one revolution. Sinceplunger 256 is raised for only the short duration of the pulse fromnetwork 194, it will be retumed to its down position by the time shaft248 has turned through one revolution. Since these cams are eccentriccircular discs, blade 370 will be moved towards and over shear block 395to cut the paper in slot 410,. and will then be returned to its initialposition by springs 384.

FIGS. 16 through 19 show the developer unit 118 in greater detail.Developer 118 includes a housing 412 which contains a quantityofdeveloper mixture 414.

Developer mixture 414 is composed of developer or v toner" powder mixedwith iron powder. Developer powder 42 in dispensed from a hopper 418through a hole 422 into housing 412 where it is mixed with iron powderto form the developer mixture 414. The developer powder may have thecomposition described above, that is, thermoplastic resin with carbonblack or light absorbing dye, etc. The particle size of the powder ispreferably between 3 and 25 microns. Also, the material of which thepowder is composed should be separated from iron in the triboelectricseries so that when the ironand developer powder particles are rubbedtogether the developer powder particles will become charged oppositelyto the iron particles and will cling to them. The iron powder particlesshould be larger than the developer powder particles, preferably beingof a size capable of passing through a 100 to 200 mesh screen.

Housing 412 has an opening 424 in its face through which a small segmentof the brush formed on 304) extends to brush across a copy paper sheet428 passing through the developer. Amagnet assembly 426 is positionedopposite slot 424 and is arranged so that brush 300 acts as its armatureand is magnetized by it.

As copy paper sheet 428, bearing an electrostatic image, is passedbetween the magnet assembly 426 and the protruding brush 300, the brush300 is rotated and picks up iron particles which arrange themselvesalong its lines of forcelike bristles. The developer powder particlescling to the iron particles in these bristles." As these bristles" arebrushed over the electrostatic-image-bearing surface of sheet 428, thedeveloper powder particles, which bear a charge opposite to that of theimage areas of the electrostatic image, are attracted away from the ironbristles and cling to the image areas of sheet 428 to form a visiblepowder image capable of being fused to make a permanent finished copy.The iron particles are held magnetically by the brush 300 until theyreach the side of the brush farthest away from magnet assembly 426, atwhich point the magnetic flux is so weak that the particles fall backinto the body of the mixture 414.

Housing 412 and developer powder hopper assembly 418 are oscillatedlongitudinally so that developer powder 420 is shaken from hopperassembly 418 into housing 412 where it is mixed and rubbed together withiron particles. A paddle as sembly 416 helps to mix and circulate themixture 414 and distributes it evenly along the length of brush 3%.

Developer powder hopper assembly 418 includes a conical outer hopperhousing 434) which is shaped like the frustum of a cone and is affixedto developer housing 412 with its bottom opening surrounding hole 422. Amovable hopper 432 is positioned in housing 439. Movable hopper 432 isshaped like hopper housing 43f) except that it is slightly shorter andits sides have a larger included angle between them. A generallyY-shaped jiggle rod 434 is positioned inside movable hopper 432 with itsstern 436 extending down through hole 422 into housing 412 to a positionnear paddle assembly 416. A lid 438 covers the upper opening of housing4-31) to prevent developer powder 424) from spilling out.

Paddle assembly 416 includes an elongated support rod 440 with a seriesof L-shaped arms 442 attached to the underside of rod 444) with theirlong portions extending downwardly. Attached to this long portion ofeach of arms 442 is a flat, rectangular flexible sheet metal blade 444which forms a paddle. These paddles 444 are aligned parallel to oneanother and at a 45 angle (see FIG. 18) with the longitudinal axis ofrod 44%. The ends of rod 440 extend through square holes in housing 412and abut against side frame members 448.

Housing 412 is slidably mounted upon the shaft of brush 300 by means ofbushings 452. The brush 300 is rotatably supported by side members 448and bushings 456.

Triangular cams 460 are affixed to the exterior of housing 412 nearshaft 298 and pins 464 extend perpendicularly from shaft 298 indirections angularly displaced from one another. When the shaft isrotated, pins 464 engage cams 460 alternately and impart an oscillatorymotion to housing 412 in a direction parallel to the longitudinal axisof brush 300. The frequency of these oscillations is advantageouslyabout 75 cycles per minute.

The ends of paddle support rod 440, by abutting side frames 448, holdthe paddles 444 stationary while housing 412 oscillates. Since paddles444 are flexible, their rear portions bend toward rod 440 when housing4E2 moves to the right (FIG. 18) and permit a quantity of developemixture 414 to pass between these paddles and the rear wall of housing412. When housing 412 moves to the left, the rear portions of paddles444 bend away from rod 440 and prevent the developer mixture fromreturning to its original position.

A similar mixing action in the developer mixture 414 is set up betweenthe paddles 444 and brush 300. The developer mixture 4l4 is thuscirculated as indicated by arrows 445 on FIG. 18 and thoroughly mixed sothat developer powder is substantially uniformly distributed in the ironpowder and properly charged by rubbing against the iron particles beforeit is captured in the brush. In addition, this distributes the mixtureevenly along the length of brush 3% and avoids piling up at either endof housing 412.

Oscillating paddles 444 hit the lower end of jiggle rod 434 and causethe bottom opening of movable hopper 432 to be alternately aligned andunaligned with the inlet hole 422 in housing 412 during each cycle ofoscillation. This causes a metered amount of powder to flow into thehousing during each cycle and makes the rate of powder replenishmentapproximately proportional to the rate of its removal from the mixture.jiggle rod 434 also stirs the powder in the hopper to prevent it fromcaking and to make it flow smoothly into housing 412.

As is shown in H65. 48 and i9, brush 3% includes a series of discs 463mounted in closely spaced relation along shaft One side 476 of shaft 293is flattened and the central holes in the discs conform to thecross-sectional shape of the shaft, assuring their accurate assembly andretention of the shaft. Each disc 468 is separated from the next disc bya washer 472.

Referring now to FIG. 16, each of the discs 468 is made of soft iron orsimilar magnetic material and each is advantageously bent along lines474, which describe a polygon, advantageously a square whose corners arelocated at the edge of disc 468. The bends along some of these lines aremade in one direction and bends along others of these lines are in theopposite direction, e.g. in FIG. 17 bends along alternate lines 474 aremade towards the observer while bends along intermediate lines 474 aremade away from the observer. The angle of these bends is fixed at avalue such that the edge of each disc describes a substantially smoothwavy curve, as is best seen in FIGS. 18 and 19. Because the discs 468have this shape, the instantaneous position of the edge of each discprogresses from side-to-side in the direction of the longitudinal axisof shaft 298 relative to any point at opening 424 when the disc isrotated. This relative motion creates a thorough brushing of the entiresurface of copy sheet 428 with developer powder.

Discs 468, which are bent along lines describing a square, create twosuch side-to-side oscillations for each revolution of shaft 298. Thenumber of these oscillations per revolution may be varied by increasingor decreasing the number of sides of the polygon along the sides ofwhich the bends are made. For example, bending discs 468 along the sidesof a hexagon would produce three oscillations per revolution instead oftwo. I

FIG. 20 illustrates an alternative brush member 3000 which can be usedin the developer unit 118 in place of brush member 300. This brushmember comprises a hollow cylinder 482 made of magnetic material such assoft iron and having a pair of spindles 484 at its ends. A perforatedsleeve 486 made of magnetic material is secured to the outside ofcylinder 484. As is indicated in the drawing, the holes in sleeve 484are staggered" with respect to one another thus leaving generallyspiral-shaped ribbons of material such as those indicated by dashedlines 488. Since the distance between magnet 426 and the brush member3006 is the least at points along these ribbons, the iron powder brushbristles tend to concentrate along these ribbons and sweep the surfaceof the copy paper 428 from side-to-side.

A brush similar to brush 300c can be produced by substituting for sleeve484 a screen comprising wires made of magnetic material. The wires ofthe screen should be aligned at an angle to the longitudinal axis ofcylinder 484 so that the wires describe spiral paths like the ribbons ofmaterial in sleeve 484.

An advantage of both of these forms of brush 3000 is that they arerelatively simple and inexpensive to manufacture while providingefficient and complete sweeping of the copy sheet.

Magnet unit 426 includes a permanent magnet or magnets 492 as well asparamagnetic members which concentrate and direct the flux. In preferredexample shown, two permanent magnets 492, which advantageously areceramic magnets, are arranged with their north poles connected togetherby a magnetic pole piece 496 their south poles connected together by asecond magnetic pole piece 498. These pole pieces are advantageously ofsoft iron. A pair of magnetic end pieces 500 are bolted to pole piece496 and nonmagnetic side supports. Members 500 each have a semicircularcutout end portion bearing against shaft 298 of brush 300, so that,together with the brush 300, members 00 constitute an annature for thepermanent magnet. In this arrangement, the lines of magnetic flux flowfrom the north poles of magnets 492 through polepiece 496 and end pieces500, through shaft 298 and discs 468, through the air gap betweenpolepiece 496 and end pieces 500, through shaft 298 and discs 468,through the air gap between pole piece 498 and the edge of discs 468,and on to the south poles of magnets 492. In this manner, a strong andevenly distributed magnetic flow is created across the air gap to createstrong iron powder bristles 427 for brushing sheet 428.

Magnets 492 are composed of permanently magnetized particles imbedded inceramic material and are manufactured under the trade name Indox V" byIndiana Steel Products Corporation, a division of Indiana GeneralCorporation. This material is made of barium carbonate and iron oxide,powdered, compressed under high pressure, and sintered. The resultingmaterial is believed to be BaFe O These magnets have advantage overother permanent magnets in that they provide a large amount of fluxdespite their elongated shape. Thus, unit 426 can be more compact andefficient than magnetic devices used previously.

A tray 506 (see FIG. l) is positioned below developer unit 118 to catchany powder which may be spilled by brush unit 118. This is a shallow,removable tray with a slot in its bottom having upwardly convergingedges 507 to permit paper to pass through the tray while preventing thepowder from falling through.

A paper guide 504 (see FIGS. land 16) is bolted to support members 448and is positioned near opening 424 in housing 412 and near theprotruding "bristles of brush Silt) to guide copy paper past the brush.

The entire apparatus will ordinarily be enclosed in a compact housingwhich is omitted from FIGS. 1-20 for the purpose of simplification.

FIGS. 21 through 24 show another embodiment of the copying machine ofthe present invention. The copying machine so illustrated a housing 508having an inlet guide 54d for a sheet of copy paper 74 and an inletguide 72d for a document 50 to be copied.

Document 50 moves down passage 72d to a pair of rolls 56d and 58d, whichfeed document 50 into exposure window 66d along the face of glass plate98d. A pair'of rolls 68d and 70d feed the document away from the window66d and out of the machine through an outlet guide passage. 1

A central lamp 100d and a pair of lamps 100d positioned on the outsideof the machine and shining through windows 536 in the housing combine toilluminate the document as it passes the window 66d. The image of thedocument is formed by focusing light which passes through the lenssystem 108d and on to a mirror 106d which reflects the image up to theimage location 93d. 1

Photosensitized copy paper, which may be of the type described above, isinserted into inlet guide 54d and moves over a charging unit 88d whichproduces a uniform electrostatic charge on the sensitized surface of thesheet. As the sheet passes to and across the screen 95d at the imagelocation 93d, it is exposed to the image of the document which inducesa, corresponding electrostatic image on the sheet. Rolls 114d and 112afeed the sheet around guide 554 and on to another pair of rolls 556, 558which pass the sheet on to a developer unit 118d where the latentelectrostatic image received at the window 93d is converted into avisible image by use of fusible developer powder in the manner describedabove. The sheet passes on through rollers-562, 564, over the supportplate 566, and under fuser unit 120d to fix the image on the sheet, andthen out of the machine through a slot as shown.

Referring now to FIG. 22, which illustrates the drive system of copymachine shown in FIG. 21, a drive motor 182d and its cooling fan 214dare mounted centrally in the housing of the machine. The motor shaftdrives a chain 220d. This chain connects the drive sprockets on rolls562, 556, 112d, and 94d, for feeding the sheet of copy paper through themachine. An idler sprocket 580 maintains the necessary tension on thechain.

The motor shaft also drives a second chain 230d which connects drivesprockets on rolls 68d and 58d with the motor shaft to feed the document50 through the machine. An idler sprocket 586 maintains tension in chain230d.

A brush drive motor unit 588 has an output shaft 590 and an output gearmeshing with a drive gear 296d on the developer brush shaft 298d todrive brush 300d.

The brush 300d of the developer unit may be the same as brush 300 orbrush 3080 described above, or may be of any similar construction.

ill

Referring again to FIG. 21, brush 300d is positioned near the. sheet ofcopy paper as it passes through the developer unit 118d. Positioned onthe other side of the sheet is a magnet unit 426d used to form thebristles" for brushing the toner powder onto the sheet.

Sidewalls 602 and 604 of developer unit 118d form a housingwhich holds asupply of iron powder and developer powder mixture 608. The mixture isapplied to the brush 300d only in the gap 606 near the bottom of thehousing, primarily by magnetic attraction. This arrangement minimizesloss of developer mixture in transit from the housing to the brush.

The brush rotates in the direction indicated by the arrow in FIG. 21 andthe bristles" which form in the magnetic field on the, lower side of thebrush, slump back onto the brush assembly near the top position. Thereleased developer mixture is guided by wall 602 back into the mixturebody 608 where it is remixed and enriched with additional toner beforebeing reapplied to the brush 300d. The uppermost edge of wall 602isl'positioned close to brush 300 to remove as much of the loose mixturefrom the brush as possible.

Toner powder hopper 41811 has a pair of converging sidewalls 612 and abottom screen 616. A pair of supports s (see FIG. 22) are provided atthe ends of this hopper to support it with respect to the brush 300d.These supports follow the side-to-side oscillating motion of thebentwashers of brush 300d and thus shake toner powder onto the brush,where it is mixed with iron powder and is carried into the developermixture body were the toner powder and iron powder are rubbed togetherand dispensed to the brush as described above. In this manner, toner isreplaced in developer mixture 603 as it is used, and at a rateproportional to the oscillations of the brush discs.

An alternative toner powder feed device is shown in FIGS. 23 and 24.This device has a hopper 41812 with converging sidewalls 622 and abottom screen 616a. The hopper is supported by members 628 at its endswhich contact the top surface of brush 300d to follow the edges of thebent discs of the brush to provide side-to-side oscillation in the samemanner as described above. Several flexible, y-shaped wires 630 havetheir stems depending through screen More to contact the surface ofbrush 300d. Wires 630 agitate the toner powder in the hopper inaccordance with the oscillation of the brush and thus facilitatedispensing the powder in a smooth and steady flow, and at a rateproportional to the oscillations of the brush.

Although preferred embodiments of the invention and certainmodifications have been set forth in detail, these are not exhaustive ornecessarily limitative; on the contrary, the showings herein-are for thepurpose of illustrating the invention and its principles so as to enableothers skilled in the art to adapt the invention in such ways as bestmeet the requirements of particular applications, it being understoodthat various modifications may be made without departing from the scopeof the invention as defined by the claims.

.1. In electrostatic printing apparatus utilizing a mixture of carrierparticles and developer powder particles in a manner such that thenumber of carrier particles remains relatively constant while the numberof developer powder particles is reduced; rotary means for distributingsaid developer powder upon a surface to be printed, drive means forrotating said rotary distributing means, a housing containing saidmixture and saiddistributing means, said housing having an upper openingfor receiving particles into said housing, means for replenishing thesupply of said developer powder particles in said mixture at a rateapproximately equal to the rate at which said number of developer powderparticles is reduced, said replenishing means comprising a developerpowder container having a lower outlet positioned to feed into saidupper openingof said housing, a resilient vibratory member positioned insaid developer powder container and having one end depending throughsaid lower outlet and through said upper opening and. into said housing,and means associated with said drive means for flexingand'vibrating saidresilient member in an oscillatory manner, at a rate proportional to therate of rotation by said drive means, each such flexing causing saidlower outlet of said developer powder container to be alternatelyaligned and unaligned with said upper opening in said housing andthereby causing a metered amount of said powder to flow into saidmixture.

2. Apparatus for bringing developer powder into contact with a surfacebearing a latent electrostatic image to be developed by said powder,said apparatus including; a quantity of developer mixture having arelatively constant number of carrier particles mixed with and carryinga relatively depletable number of particles of said developer powder; anelongated member for brushing said powder particles onto saidimage-bearing surface; a housing for containing said mixture near saidbrushing member; means for replenishing said powder to replace theparticles brushed out from said mixture, for thoroughly mixing saidcarrier particles with said powder particles, and for distributing saidmixture evenly along said brushing member, said replenishing mixing anddistributing means including an elongated support member disposed insaid housing substantially parallel to said brushing member, a pluralityof vanes, each of which is affixed to said support member at an acuteangle with said support member and said brushing member, means foroscillating said housing with respect to said vanes in the direction ofthe longitudinal axis of said support member, a developer powdercontainer having an outlet positioned above and directed into the bodyof said mixture, and a resilient vibratory member positioned in saidcontainer and having one end depending through said outlet.

3. In an electrostatic printing device utilizing developer powder mixedand transported in a medium of magnetic particles, apparatus utilizablein association with a source of magnetic flux for bringing said powderinto intimate contact with a surface bearing an electrostatic image tobe developed by said powder, said apparatus comprising; an elongatedmounting spindle; and a plurality of generally washer-shaped membersmade of magnetic material and mounted in series at spaced intervalsalong said spindle, each of said members being bent along linesdescribing the sides of a polygon, each of said lines having its endsterminated at the outer edge of said member, successive ones of thesebends being made in opposite directions so that said outer edge of eachof said members oscillates, with respect to a fixed reference point, ina direction generally parallel to the longitudinal axis of said spindlewhen said spindle and said members are rotated together.

4. In an electrostatic printing device utilizing developer powder mixedand transported in a medium of magnetic particles, apparatus utilizablein association with a source of magnetic flux for bringing said powderinto intimate contact with a surface bearing an electrostatic image tobe developed by said powder, said apparatus comprising; an elongated andgenerally cylindrical mounting spindle having a flatted surface; aplurality of washers, each of which is made of magnetic material and hasa central cutout portion whose outline generally conforms to that ofsaid spindle, said washers being mounted in series through said cutoutportions at spaced intervals upon said spindle, each of said washersbeing bent along lines describing the sides of a square having each ofits four corners terminated at the outer edge of said washer, successiveones of these bends being made in opposite directions so that said outeredge of each of said washers oscillates, with respect to a fixedreference point, in a direction generally parallel to the longitudinalaxis of said spindle when said spindle and said washers are rotatedtogether.

5. In an electrostatic printing device having a magnetizable rotarybrush member for brushing a mixture of magnetic particles and developerpowder onto a surface bearing an electrostatic image to be developed bysaid powder; the surface of said brush member being adapted toeffectively oscillate with respect to the longitudinal axis of saidbrush member as said member is rotated; apparatus for supplying saidmixture to said brush member, said apparatus comprising; a housing forcontaining said mixture near said brush member, mixing said magnetparticles with said powder, and providing a metered supply of saidmixture to said brush member, said housing having a relatively wideinlet opening, an upper edge positioned close to the outer edge of saidbrush member at a position relatively remote from the position at whichsaid outer edge brushes said image-bearing surface, said housing edgebeing utilized for scraping magnetic particles from said brush memberafter said powder has been transferred from said particles -to saidsurface to be developed and directing said scraped particles into saidinlet opening, said housing also having a relatively narrow outletopeninglocated below said inlet opening and adjacent said edge of saidbrush member at a position just preceding said position at which saidimage-bearing surface is brushed, said outlet opening serving to meterthe flow of said mixture to said brush member; and developer powderstorage and dispensing means positioned above said housing inlet forfeeding metered amounts of said powder into said housing to be mixedwith said magnetic particles as they are scraped from said brush member,said powder storage and dispensing means including means responsive tosaid oscillations of said brush surface for agitating said powderstorage and dispensing means and metering the flow of said powder tosaid housing.

6. in an electrostatic printing device having a magnetizable rotarybrush member for brushing a mixture of magnetic particles and developerpowder onto a surface bearing an electrostatic image to be developed bysaid powder; the surface of said brush member being adapted toeffectively oscillate with respect to the longitudinal axis of saidbrush member as said member is rotated; developer powder storage anddispensing apparatus, said apparatus including a housing having anoutlet opening directed into the body of said mixture, said outletopening having dimensions such as to prevent passage of said powdertherefrom until said housing or said powder is agitated; and meanscoupled to said housing and said brush member for transmitting theoscillations of said brush member to said housing and thereby providingflow of said powder from said outlet to said mixture in meteredincrements occuring at a rate corresponding to the rate ofisaidoscillations.

7. In an electrostatic printing device having a magnetizable rotarybrush member for brushing a mlxtureof magnetic particles and developerpowder onto a surface bearing an electrostatic image to be developed bysaid powder; the surface of said brush member being adapted toeffectively oscillate with respect to the longitudinal axis of saidbrush member as said member is rotated, developer powder storage anddispensing apparatus, said apparatus including a housing having anoutlet opening directed into the body of said mixture, said outletopening having dimensions such as to prevent passage of said powdertherefrom until said housing or said powder is agitated, and meanscoupled to said brush member and extending through said outlet openingand into said powder supply for agitating said powder in accordance withthe oscillations of sad brush member and providing flow of said powderfrom said outlet to said mixture in metered increments occurring at arate corresponding to the rate of said oscillations.

8. In an electrostatic printing device utilizing developer powder mixedand transported in a medium of magnetic particles, apparatus utilizablein association with a source of mag netic flux for bringing said powderinto intimate contact with a surface bearing an electrostatic image tobe developed by said powder, said apparatus comprising: acylindrically-shaped member made of magnetic material; a sleeve made ofmagnetic material and secured to the surface of said member, said sleevehaving a plurality of holes in it; and means associated with said memberfor supporting said member for rotation about its central axis.

9. in an electrostatic printing device utilizing developer powder mixedand transported in a medium of magnetic particles, apparatus utilizablein association with a source of magnetic flux for bringin said owderinto intimate contact with a surface bearing an e ectros atic image tobe developed by said powder, said apparatus comprising; acylindrically-shaped member made of magnetic material, a screen securedto the surface of said member, said screen including wires made ofmagnetic material, said wires being aligned generally transversely tothe longitudinal axis of said member, and means at each end of saidmember for supporting said member for rotation about its central axis.

